Hi, what's up? Is the forum not very active these days? The dates of last posts seem pretty few and far between. Anyway, I've not been here for years, myself. I'm just getting my new kit together to do some wild camping, and I have a question about a project for a modified alcohol stove.
I've used Trangias and one or two pop-stoves, and was going to make another when I found small aluminium screw-top jars online, about 5 cm across and 2 high, with plastic foam inserts to seal. I bought a few and stuffed one of the bases with rockwool and a bit of mesh to cover. It burned ok just like that, but with the whole of the top burning it was undirected and easy for the breeze to push about. It needed jets...like penny stoves and other pop-can stoves...
So I had the idea of using one of the tops on it, with a smaller hole cut in the centre (ditching the plastic foam insert) - another lid with insert could be put on to store unburned fuel. How big to make the centre hole?...
I then had the idea of dishing the lid downwards, but pushing up to make the hole, creating a little depression in a ring around the hole, so I could put a small amount of alcohol in it as a primer and not have to fill the whole stove. If the screw thread sealed the container (without the plastic stuff), pressure would build up as it heats and create a single jet in the middle. I tested the seal by putting one in a jug of hot water to see if bubbles came out of the screw area, and none did, so it's feasible.
I dished the top and poked a hole from inside as planned. Now, here's the problem: if this hole is made big enough, presumably it gets to being much like an open dish of fuel (with or without wick) burning without a build-up of pressure. But if it's too small a hole, could it heat up too much and create enough pressure to explode, or could the enclosed ethanol/air mixture get to combustion proportions and explode for that reason?
I know a similar container (paint can with hole in the lid) full of gas burning from the hole gets to that point and blows the top off, because it was a school physics demo, but that's with whatever gas bunsen burners use, and alcohol might not do the same thing.
It's possible that once burning, as the pressure increases from the heat of the flame, the flame will exhaust faster and thus direct heat away from the stove more, and thus it'll be self-regulating, or it may just be impossible for pressure to build up in such a situation because the vapour can escape so fast.
On the other hand, if it acts like the bunsen gas in a can, yikes.
Any thoughts? I could just go for the safe option of a moderate sized hole, but I imagine that just being a slower version of the whole tin open at the top, still being blown about because of no pressure build up. It's tempting to try the jet version, but I don't want to have an accident ... when I'm solo wild camping.
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Originally Posted by Ehecatl
